The present invention relates to a router bit useful to trim a composite material made by impregnating resin into laminated cloth made of carbon fiber or Kevler (trademark).
Since such a composite material has high weight and high strength, the material is used for making the body of an aircraft or vehicle. The characteristics of the composite material is varied dependent on the type of combined materials, treatment temperature, construction and other factors. Therefore, it is very difficult to cut the composite material.
FIG. 6a shows a section of material b in trimming with a right-hand router bit a, FIG. 6b shows a section with a left-hand router bit a' and FIG. 6c shows a section with a strait fluted bit a". In the trimming with the right-hand router bit a, fluff and burrs are left on the surface of the material, and with the left-hand rooter but a', fluff and burrs are left on the underside of the material, and with the straight fluted bit a", fluff and burrs are formed on both sides. In addition, a distance between the position of the trimming and an edge of a clamping jig c must be provided. Accordingly, the material vibrates about the trimming portion, which causes delamination, a decrease of strength and fatigue fracture of the composite material.